1. Field of the Disclosure
The disclosure relates to a display; more particularly, the disclosure relates to a head-mounted display (HMD).
2. Description of Related Art
With the continuous progress of displays or display-related technologies, the displays tend to be become light and compact to satisfy users' requirements for portability of the displays. For instance, a head-mounted display (HMD) is one of the light and compact displays. The HMD normally allows a user to observe a video signal through a pair of glasses, a pair of goggles, or a wearable helmet. Due to the inherent limitations of crystalline lens and ciliary muscle of a human eye, the area or the extent of space visible to the human eye (i.e., the minimum visible distance) is restrained. When a distance to a to-be-observed object is shorter than the minimum visible distance of the human eye, i.e., when the object is overly close to the human eye, the image of the object formed on a retina of the human eye is of insufficient clarity. Hence, the human eye is not able to see the object clearly. In view of the above, the display in a conventional HMD system is set to be apart from the human eye at a certain distance, so as to resolve the aforesaid issue that the human eye is not able to clearly observe the information displayed by the HMD. Said HMD, however, is bulky and is difficult to be worn by a user. If the volume of the HMD is reduced by shortening the distance between the HMD and the human eye, the human eye can barely see the image with clarity; what is more, the overly short distance may lead to contraction of ciliary muscle over a long period of time, and thereby the problem of eye fatigue or blurred vision may occur. Accordingly, how to effectively reduce the volume of the HMD and keep the observed image clear is one of the most imperative issues to be resolved in the industry.